Machine tool



A. A. SCHWARTZ 2,344,420

MACHINE TOOL Filed May 9. 1941 5 sheetssheet 1 INVENTOR Arm/m4. 52/24/0/ ATT March 14, 1944.

| x I L March 14, 1944. A, SCHWARTZ MACHINE TOOL v Filed May 9, 1941 5 Sheets-Sheet 2 w w. m Twu MM N Q m4 w .4 $4 A \RQ Q N NM March 14, 1944. A SCHWARTZ 2,344,420

MACHINE TOOL Filed May 9, 1941 5 Sheets-Sheet 3 March 14,1944. A. A. SCHWARTZ MACHINE TOOL Filed May} 9, 1941 "5 Sheets-Sheet 4 vim BY Q5440,

March 14, 1944.

i A. A. SCHWARTZ I MACHINE TOOL 5 Sheets-Sheet 5 Patented Mar. 14, 1944 iJNlTED STATES .rArENT omen Arthur A. Schwartz. Buffalo, N. Y., assignor to Bell Aircraft Corporation, Buffalo,- N. Y.

A plication May 9. 1941, SerialNo. 392.71 3 Claims. (01. 51419)- This invention relates to a novel counter-sinking bit and to novel apparatus and a novel method for producing the same; the novel machine of the invention being susceptible of employment in other analogous fabricating operations.

An object of the present invention resides in the provision of a novel counter-sinking bit wherein the cutting lip is presented to the work obliquely whereby the material is sheared from" the object being operated "upon.

A further object of the invention resides in the provision of a novel machine tool having a rotatable abradingor other material removing implement with means for presenting a work piece or blank thereto for formation of my novel counterdetails-of constructionof the'exemplary embo'di ment illustrated in' the drawings andhereinafter described, together with the statements concerning the mode of operation included in. the de scription.

While specific details of construction and oper- V ation are set forth" in theafollowing by way "of" example, it is to be understood that my invention"? is not to be considered as limited thereto or otherwise than as defined in the appended claims.

Fig. 1 is a general plan View of one form of'the machine of my invention;

Fig. 2 is a vertical-cross sectional view'takenapproximately on the line II--II of Fig. 1;

Fig. 3 is an elevational view of the grinding apparatus with the base of the-machine shown fragmentarily in crosssection; v r

Fig. 4 is a cross sectional View taken approximately on line IV-IV' of Fig.1;

Fig. 5 is a partial crosssectional viewtaken on the line V-V of Fig.1 and showing means 'for' dressing the grinding wheel and automatic means for operating the dressing means;

Fig. 6 is a detailed elevational view taken ap'-.

proximatelyas indicated by the line"VI'VI .of' Fig. 3 showing means for feedingthe grinding apparatus in adirection transverse to its axis ofrotation-for cooperation with the wheel dressing means; I

Fig. 7 is a" schematic view comprising a wiring diagram depicting the circuits provided for auto matic: operation of the grinding wheel dressing means andthe transverse feed for the grinding apparatus; i r

Fig: 8' is-a-detailed .viewof a micro-switch for controlling; the circuits of Fig; 7, together with an operating cam therefor;

Fig. 9 is a developed schematic view of the profile of a tool position controlling' cam;

' Fig. 10 is a fragmentary plan view of the chuck.

portion" of .the machine of my invention with a modified cam element and bit supporting means, for operating-upon the novel bit element of my invention;

Fig. ll is a further ,modified'chuck and cam control element therefor for performinganother' operation in the fabrication of the novel bit of my invention; and;

Fig. 12 is an end elevational view of thechuck of Fig.- 10 with the novel bit of my invention held therein and viewed 'from'itswork' contacting end;

Throughout'the. several figures of the drawings like characters of reference denote like parts and the numeral lfl'indica'tes generallya supporting base for the machine of my invention,'such base havingpreferably a flat upper surface plate portion H for supportinga work piece holder designated generally l2 and a grinding apparatus designated generally and arranged to operate upon the work piece.

The grindingapparatus comprises a driving motor I5 and'a grinding wheel [6 having a peripheral grindingface and preferably disposed for rotation coaxia-llywith the motor 15 as by being secured directly to a motor shaft H in conventional manner. The assembled motor 15 and wheel l6 may be'adju'stably moved on the surface plate portion-I l of the base) in the direction of the axis of'the' motor and wheel by the pro visionof'an intermediate" plate 18'. portion of the'interniediate plate axially along 'th pl'at 1afin' guidedrelatio'nQ Accurately adjusted'position journal pOrtionQf-of-a 'scre'v'v22 may havebearmg. Axialfmovem'ent of the screw 2l with respect to theflugi-zfl' maybepre vented 'by thejproto'the screw, the

vision of collars 23 and '24 fixed The upper 18 am thaba'se of the casing of the motor I 5 are complementarily formed "whereby the motor" l5 m'ay be moved of them'otor' I5' along the platewfmay be attained by providing an upstanding lug 20 'onthe" pl'ate lfl in which a latter conveniently serving to calibrate adjustment by virtue of graduations 25 provided thereabout. The threaded portion of the screw 22 engages a threaded opening 25 in the base of the casing of the motor l and this threaded engagement may be adjusted to move the motor axially by manipulation of a hand wheel 21 secured to the outer end of the screw 22.

I The grinding wheel 16 and its driving motor are further adapted to be moved along the base II) in a direction at right angles to their joint axis of rotation to compensate for dressing of the grinding wheel. The instrumentalities provided for such transverse adjustment will be hereinafter described.

The work supporting means, designated generally [2, comprises essentially means for rigidly supporting a piece to be operated uponby the grinding wheel l6 or any other abrading element which may be substituted therefor. The piece to be operated upon may bein the nature of a twist drill, a countersinking bit, or any other analogous work piece requiring similar grinding treatment. It is desired to support the Work piece in a readily releasable manner so that,

. while the axis of the drill bit or other work piece is maintained in a common horizontal plane with the axis of the grinding wheel, the work piece may be moved in various directions in a horizontal plane. Such movement is required for proper presentation of the drill bit-or other work piece to the grinding wheel.

To this end the work supporting means [2 includes a bottom plate which-has a fixed pivot with respect to the base I0. This pivot may comprise a pin 3| extending through concentric apertures in the plate 30 and the upper surface plate H of the base Ill. The pin 3|, in the. form illustrated, includes a head 32- and a threaded end provided with a nut 33 which cooperates to retain the plate 30 in assembled pivotal relation with respect to the'base Hi.

[The plate 30 has, at a point spaced substantially from its pivot pin 31, a downwardly projecting, preferably circular. boss 34 which extends through an arcuate slot 35 formed in the upper surface plate II of the base ID. This boss 34 receives a journal portion of a pivot pin 35 which has a threaded end 3'! for rigid assembly of the pivot pin 36 with respect to a plate 40 which is preferably circular and disposed upon the plate 30 for pivotal movement with respect thereto upon the axis of the pivot pin 36. The plate 40 in turn supports a mounting block 44 which has'a horizontal, longitudinally extending opening for receiving any of a variety of drill bit or other work piece chucking means, one of which is'designated generally 41 in Figs. 1 and 2.

The lower surface of the mounting block 44 and the upper surfaceof the circular plate 40 are complementarily grooved, as indicated at in Fig. 4, whereby the former may be moved along the circular plate 40 in the direction of the axis of the chuck receiving opening in the mounting block 44. The means, for releasably retaining therespective parts of the work piece holding means l2 in their variously adjusted positions will be alluded to presently.

The chucking meansdesignated generally 41 comprises an outer shell or sleeve which is rotatably disposed in the axial opening in the mounting block 44 and has a reduced tapered portion 61 atone end thereof, see Fig. 2. At its opposite end the sleeve 60 has associated therewith an annular knob 62 which may fit into a counterbored opening in the adjacent end of the sleeve 60, as at 64, for being rotatably supported thereby. The knob 62 has an annular groove 65 therein and the inner end of a screw 66 carried by the sleeve 60 engages such annular groove to prevent axial displacement of the knob 62 with respect to the sleeve 60 while at the same time permitting free rotative movement.

The knob 62 is interiorly threaded to cooperate with threads formed upon a sleeve 68 which is carried within the sleeve 60 for free axial movement with respect thereto. It will be noted that rotative movement of the knob 62 causes axial sliding movement of the sleeve 68 in the sleeve 60, relative rotation of the former with respect to the latter being prevented by engagement of the inner end of a screw 10 in an axially extending groove 1| formed in the sleeve 68. The screw 70 is threaded into the wall of the sleeve 60.

By moving the sleeve 68 axially to the left as viewed in Fig. 2, by manipulation of the knob 62, the left-hand end of the sleeve 68 may be brought to bear against a plurality of segmentally arranged chuck jaws 12 which cam against the inner surface of the tapered end 6| of the.

sleeve 60 and thereby grip a Work piece, as for instance a drill bit 15, in a conventional manner.

The opposite end of the dril1 bit 15 may be centered and supported by a spring collet disposed in a sleeve 8| which has an enlarged bearing portion 82 disposed for free axial movement Within the sleeve 68. The collet 8!] is normally retained in a gripping position with respect to the drill bit 15 by virtue of a coil spring 84 which acts between a collar 85 formed on the sleeve BI and a headed portion 86 carried by a stem 87 which is rigidly associated with the spring collet fingers 80. The spring collet assembly is conventional and has as its chief function the support of the work piec during its introduction to the chuck jaw 12 from the right as viewed in Fig. 2.

As illustrated in Fig. l the entire work piece supporting means, designated I2 and comprising principally the chuck 41, the mounting block 44, the circular pivot plate 40 and the swinging base plate 30 are shown in such position that the axis of the chuck 41, and consequently of the drill bit 15, extends at an angle of 45 with respect to the peripheral face of the grinding wheel adjacent the point of contact of the frusto-conical point of the drill bit 15 therewith. Thisangular relationship is attained by swinging movement of the base plate 30 and all of the other parts of the work piece supporting means which are carried thereby on the pivot pin 3|.

It will be noted that in the exemplary embodiment now being described the axis of the pivot pin extended is substantially tangent to the periphery of the grinding wheel l6, although variation of this relationship may be brought about by adjustment of either the grinding means I3 or the Work holding means l2 or both. Adjusted pivotal position of the work holding means I2 about the pivot pin 3! may be maintained by a locking screw 90 threaded into the base plate 30 and adapted to engage, frictionally or otherwise, with the top of the surface plate ll of the base Ill. A knurled manipulating knob 9| for the screw 90 is shown in Fig. 2 and an extension 93 of the base plate 30 may carry the screw 90 and terminate outwardly in an indicating portion 94 for cooperation with a graduated quadrant plate 95 which may besecureddire'ctly to the surface plate II of the'base I9. This adjustment, in the case of the grinding of the generally conical end of a twist drill determines the angle of the cutting lip with respect to the axis of the drill.

Means are provided whereby the chuck 41 and the mounting block 44 may be swung'toward and away from the grinding wheel, for a purpose which will presently appear, without disturbing the primary adjustment of'- the angular relationship of the axis of the work as such angular relationship is defined by the adjusted swinging of the base plate 39 on the pivot pin'3I. Such independent pivotal movementis attained by virtue of the circular plate 49 which is pivotally supported upon the base plate Why the pivot pin 39 and permits pivotal movement of the chuck '41 to a position where the point of the drill may be introduced to an aligning element shown at 98 in Fig. 1.

This aligning element 98 includes a pair of spaced pins 99 which are adapted'to engage the opposed flutes of a drillbit and by such engagement insure that the angular disposition of the drill, with respect to its own axis, is such that its cutting lips extend horizontally. The pins 99 may be rigidly supported by a plug I99 disposed for axial sliding movement in the upper end of a post I9I secured to the base plate 39. The plug I9I has a reduced stem I92 extending rearwardly therefrom and terminating in a manipulating member I93. A compression coil spring I94 is disposed about the stem I92 and acts between the back of the plug I99 and a bracket I95 carried by the post I9I to urge the plug E99 and the guide pins 99 resiliently forwardly to the position illustrated. After the bit has been angularly aligned and secured in the jaws of the chuck 41 the guide pin 99 may be manually withdrawn against the resistance of the spring I94 to permit pivotal movement of the work piece to the grinding wheel IS on the pivot pin 36. Pivotal movement of the chuck 91, the mounting block 44, and the plate 49 on the pivot pin 36 is limited by engagement of a pin I91, which is fixedly carried by the plate 49 in an arcuate slot I98 formed in the upper surface of the base plate 39. Engagement of the pin I91 against the ends of the slot I98 defines the limits of pivotal movement about the pivot pin 36.

utomatic means are provided for dressing the peripheral face of the grinding wheel I6 between grinding operations and such means include, in addition to the wheel dressing means proper, means for automatically feeding the grinding mechanism in a horizontal direction transverse to the axis of rotation of the wheel I6. To this end the intermediate plate I9 which supports the motor I5 and the grinding wheel I6 for movement thereon in the direction of the axis of rotation of the grinding means, is itself disposed upon the upper surface plate II of the base I9 for sliding movement in a direction transverse to the axis of rotation of the motor I5 and the grinding wheel I6. The intermediate plate I8 has rigidly associated therewith a block III] which extends downwardly through an elongated slot II I in the surface plate II and is internally threaded for cooperation with an adjusting screw H2. The adjusting screw H2 is journaled in a pair of bearing blocks II3 which are secured to the under side of the portion II of the base I9 and the adjusting screw II2 may be held against axial movementin.any-zconvenient manner.

Adjusting rotation of the screw H2 is accomplished by means of a drivecomprising a worm wheel II'4 which is fixed thereto, a worm II5 journaled in suitable bearings at the underside of the plate II and fixed for rotation with a ratchet wheel 1. Increments of rotation are imparted to the ratchet wheel II1 by a pawl II8 carried by a pawl arm I I9, the latter being oscillated by alternate energization and de-energization of a solenoid I29. Return movement of the pawl arm H9 and the pawl H9 may be accomplished by a spring I2I upon de-energization of the solenoid I29. A link I22 connects pivotally between a movable core I23 of the solenoid I29 and the pawl arm I i9.

The solenoid 129 appears in the wiring diagram, which is Fig. 7, and has an operating cir-' cuit B23 in parallel with the principal motor circuit. A cam I24 is fixed to the pivot pin 36 which pivotally associates the circular supporting plate 49 of the drill holding chuck 41 with the base plate 39. From this it will appear that each partial rotation of the circular plate 49, the mounting block 4- -5 and the chuck to a position for aligning a drill bit by use of the gage 98 results in a partial rotation of the cam I24 to to close a micro-switch I25 in the circuit I23 and energize the solenoid I29.

The cam 524 is viewed from the bottom of the machine in Fig. '1 and in the position which'it assumes when the chuck 41 is in the angular position illustrated in Fig. l. The first part of the pivotal movement on the pivot pin 39 to bring the bit 15 to the gage 98 causes the first rise of the cam I24- designated I26, to close the switch I25. After closure of the micro-switch i25, continued rotation of the cam I24 during which time the drill bit completes its movement to the gage 93, results in the closure of a second micro-switch I21 and the resultant energization of a second solenoid I 28 likewise arranged in shunt relation with principal motor circuit of the machine by a shunt circuit I29, the closure of the second switch I21 being effected by a further rise I39 on the cam I24. Such second sol-enoid I28 is shown in Figs. 2 and 5 as carried at the underside of the plate II by a bracket I3I which may be retained by the same nut 33 which secures the pivot pin 3! of the base plate 39.

The pivot pin 3i has its head 32 bifurcated to pivotally support an arm 32 which is provided at its outer. end with a grinding wheel dressing tool, in the nature of a diamond or the like, I34. The wheel dressing tool I34 may be adjustably supported by a screw I35. It will be noted that the solenoid I29 has an armature or core I36 provided with a stem I31 which extends through the pivot pin 3i and is pivotally connected to the arm I32 eccentrically to the pivotal mounting thereof as at I38. A spring I39 is provided for normally, that is during periods of de-energization, urging the various movable elements of Fig. 5 to the position there shown.

Energization of the solenoid I28 exerts a downward pull upon the stem I31 and tends to oscillatethe arm I32 in a manner intended to draw the tool I34 across the peripheral face of the grinding wheel IE to dress the same.

Obviously the normal high-speed action of a solenoid would result in too rapid an oscillation of the arm I32 to adequately dress the periphery of the wheel. For this reason a dash pot I49 is preferably associated with the solenoid I28 to slow its action to a rate calculated to properly dress the periphery'of the grinding wheel.

The dash pot I40, Fig. 5, may comprise a chamber filled with a fluid of proper viscosity and having therein a piston I4I operatively connected with the core or armature I36 by means of a stem I42. The piston, in Fig. has a slow bleed hole I43 and a quick return check valve I44.

It will be noted that the degree or depth of dressing depends on the amount of transverse feed which has been imparted to the grinding apparatus by rotation of the screw II2 immediately prior to the dressing operation and that the two steps, advancement of the grinding wheel transversely of its axis and passage across its periphery of the dressing tool, are effected automatically and successively during movement of the chuck 41 to the gage 98 to properly align a bit or other work piece.

With the commencement of the actual bit or tool grinding operation, it is desired that axial disposition of the bit or work piece and movement thereof during grinding be accurately determined and controlled by the relative angular disposition of the bit with respect to its own axis. To this end cam means are provided for varying the axial disposition of the bit by and upon rotation thereof to change the immediate zone of angular contact of the point of the tool with the grinding wheel. Such cam means may comprise a readily removable and interchangeable face cam such as is indicated at I50 in Figs. 1 and 2. The general profile of the radial face of the cam I50 appears in Fig. 1 and a development of this profile, wherein the full 360 of its periphery is developed into a single plane to show its camming contour, is shown in the schematic view, Fig. 9.

The cam I50 may have an annular seat for engaging over and bearing upon a boss I5I formed on the mounting block 44 co-axially with the opening for receiving the sleeve 60 of the chucking means 41. Axial displacement of the cam I 50, after it is in position, may be prevented by means of a screw I52 whose head I53 engages in a slot in the periphery of the cam I50, and to permit ready assembly such slot may be of the bayonet type so that removal of the cam I50 may be efifected by a partial rotation whereby the head I53 of the screw I52 comes int registry with the entrance portion of the bayonet slot.

Accurate angular disposition of the cam I50 with respect to the mounting block 44 is brought about by engagement of a key portion I56 of a lever I51 in a peripheral pening in the cam I50. Lever I 51 is pivotally supported between bearings I59 which may be integral with the mounting block 44 and the lever I51 has an oppositely extending arm I60 which pivotally engages the end of a second key I6 I.

Initial assembly of the cam I50 upon the mounting block 44 is accomplished with the lever I51 lifted to permit entry of the cam I 50 beneath the key portion I56 of the lever I51. Such manipulation of the lever I 51 may be facilitated by the provision of a knob or other handle means I66. At that time the other key I6I will be engaged in a lengthwise key seat I64 formed in the sleeve 60 of the chucking means 41. Engagement of the key I6I in the key seat I64 determines the angular disposition of the sleeve 60 and consequently of the entire chucking means 41, and in this way accurate initial disposition of a ball cam follower I16, which may form a part of the 'screw 10, is assured.

The flutes of the drill are engaged with the pins 99 of the gage 98 and the drill is tightened in the jaws 12 of the chuck 41 with its cutting lips extending horizontally while the key I6I is engaged in the key set I64, whereby proper angular relationship between the cutting lips of the bit and the cam follower I10 is assured. After initial introduction of the cam I50 to the boss I5I and accurate securement of the bit or work piece in the chuck 41 the cam I 50 is moved angularly until its peripheral opening registers with the key portion I56 of the lever I51, whereupon the latter is dropped to the position shown in Fig. 2. 7 p

The entire assembly comprising the bit 15, the chuck 41, the mounting block 44, and the circular plate 40 is now ready to be moved about the axis of the pivot pin 36 to present the bit to the grinding wheel. Preparatory to such movement the gage pins 96 are withdrawn to avoid interference with swinging movement of the end of the bit'15.

In this position of parts, as has been stated, the drill 15, for instance, is disposed with its cutting lips extending horizontally. With respect to a point grinding operation,-this disposition of the drill bit 15 would constitute a position most remote from the surface of the grinding wheel I6, with respect to movement of the drill or bit along its axis toward and away from the grinding wheel. To put it another way, subsequent grinding of the lip clearance at points thereon other than the actual cutting lip would require movement of the drill bit toward the grinding wheel. Such movement is under the control of the cam I56 and is determined thereby.

It will be noted that clockwise rotation of the chuck 41 in its receiving opening in the mounting block 44 will result in the cam follower I10 riding down the incline of the profile of the cam I50 from the positions shown in Figs. 1 and 9. The angle of this incline on any particular cam is arranged to be suitable to the grinding of lip clearance of a particular angle and as many cams I50 may be provided as there are different lip clearance requirements, where the provision of lip clearance upon twist drills is the particular problem at hand.

It is sometimes desired, after an initial grinding to grind deeper along the lip clearance of a drill, usually because the first grind has not removed sufiicient stock to complete the newly ground lip clearance surface. Means are provided so that an operator may, when this becomes necessary, release the mounting block 44 from its initially locked position with respect to the circular plate 40 for limited axial movement along the tongue and groove connection 50 between those two elements. Such release is effected by manual vertical movement of a stem I1I which has a manipulating portion I12 and a locking pin portion I13 which normally engages in coaxial openings in the upper surface of the circular plate 40 and the inner end of a pivotal arm I14.

The pivotal arm I14 has oppositely projecting pintles I15 which engage in opposed bearings formed in an upward extension of the circular plate 40 and a cooperating cover plate I11. A spring I18 normally urges the pin I12 into looking position. Release of the pin I13 from engagement with the opening of the circular plate 40 permits pivotal movement of the arm I14 upon its pintles I15 and upon such movement a lateral extension I of the arm I14 engages the opposite side walls of an opening I8I formed in the side of the mounting block 44. The opening I8I is shown in Fig. 4 as having substantial vertical clearance with respect to the lateral projection 180 but is'accurately fitted to such extension in ,ahorizontal direction. For'this reasontaccurate axial adjustment of "the'mounting block 44 on the circular plate 90 may be effected by pivotal manipulation of the arm I14.

In the form thus *fardescribed reference has been had chiefly to the use of the novel machine of my invention in the operation of grinding the drilling pointsof conventionaldrill bits. It is my invention that this machine be an all-purpose apparatus for operations of this general,

nature and, as is clear from the foregoing description, the particular chucking means, 47 and associated control cam I50 is readily removable and replaceable by other kinds of chucks for holding other kinds and "sizes of'bits, other machine tool cutters, or analogous work pieces, and suitable control cams therefor.

'Bythe substitution of'suitably modified chucks ;-and control cams, the machine thus far set forth serves in carrying out a'novel method of producing a novel countersinking bit of my invention, and reference is had to Figs. '12 through 14 wherein such bit and the modified chucking and cam control elements employed in producing the bit in the machine of my-invention are shown.

Stated generally, the novel countersinking bit of my invention is such that the pair of cutting lips thereof lie wholly in afrusto conical surface of revolution. This much, of course, is true of the cutting lips of conventional drill bits and conventional countersinking tools. The disposition of the cutting lips of the bit of the present invention isnovel, however, in the fact that'they extend in a receding helical or spiral line along such conical surface of revolution, beginning at their inner extremities and receding gradually and substantially uniformlyin such manner that 'a very substantial included angle is defined by lines radiating from the center of the bit and extending, respectively, through the beginning and end of each'cutting lip (the end being at'the' outer diameter of the bit).

As appears from a consideration of Fig. 12, the cutting lip thus formed has a scimitar-like cutting edge which results in a pronounced shearing action in the removal of metal or the like when the countersinking bit is performing its intended operation. This countersinking bit has been found to be vastly superior in ease of operation, quality of work produced, and tool life, as compared with conventional countersinking bits.

Referring to Fig. 10, mounting block 44 of the previously described machine is shown fitted with a chuck I90 which comprises merely a round bar adapted to accurately fit the axial opening which, in the previously described modification, received the chuck 41. Such bar is provided with an eccentric opening adapted to receive a bit supporting element HI and the bit blank to be operated upon to produce the novel countersinking bit of my invention is shown in Fig. at I 92. Such bit blank I92 may have a threaded shank I93 for being screwed into the end of the element I9I.

In Fig. 10 a grinding wheel is schematically indicated in dot-and-dash lines at I95, and the periphery of such grinding wheel is shaped approximately as there shown. A special cam I9? is provided for the operation which is intended to be performed with the arrangement of Fig. 10. This operation comprises the production of helical or spiral flutes in the conical face of the bit blank I92.

As originally formed, the bit blank 92 is providedwith a small, flat, circular end I 93. The flute to beformed in the frusto-conical fac of the bit blank 192 is slightly undercut whereby the angle of rake presented to the work is somewhat 'less than in conventional drilling operations.

Such under-cutting is provided by forming the periphery of the grinding wheel I 95 with a much less radius of curvature at one side than at the other, all as'shown in Fig. 10, together, of course, with a suitable adjustment of the angular disposition of the axis of the bit blank with respect to the axis of rotation of the-grinding wheel I 95. From the position there shown the operator,

in producing one of the flutes designated I98 in Fig. 12, manually rotates the chuck I in a direction which is clockwise as viewed from the :right in Fig. 10, or counterclockwise as viewed in and is accompanied by a movement of the bit blank I92 away from the periphery of the grinding wheel I in a direction at right angles to the axis of the bit blank. This latter movement comes as a result of the eccentric disposition of the bit blank I92 with respect to the'axis of rotation of the chuck I90, and is likewise in fixed relation with respect to manual rotation of the chuck I90.

The cam I91, with its follower I99, and the eccentric disposition of the bit blank I92, cooperate to present the frusto-conical surface of the bit blank I92 to the periphery of the grinding Wheel I95 in such manner as to progressively produce a flute of conical, spiral form, as shown in Fig. l2,'beginning at the central flat face I93 of the bitblank I92'and terminating at the outer diameter thereof.

After one such flute has been formed, a pin 202, which extends through the chuck I99 and the element I9I to normally prevent relative rotation therebetween, is removed and the element I9I with the bit blank I92 is rotated through 189, whereupon the pin 292 is replaced and the parts are in position to produce a second flute I98 spaced from the already formed flute.

Subsequent to the production of the two flutes I98 the remaining unground surface of the frustoconical portion of the bit blank I92 is provided with lip clearance in a manner which is substantially the same in principle as that which was described in connection with the grinding of lip clearance on conventional drill bits hereinbefore. The lip clearance of the countersinking bit of my invention is preferably somewhat less than in standard drill grinding practice. This is more than counteracted by the substantially less angle of rake provided in producing the flutes I98.

Because of the disposition of each cutting lip of the countersinking bit of my invention, wherein such cutting lip recedes spirally around the conical surface of revolution in which it lies in its extent from the center to th outside of the bit, grinding the lip clearance in the manner described in connection with conventional drill bits results in a greater grinding off of the cutting lip as the outside of the tool is approached.

For this reason grinding the lip clearance of the tool decreases the included angle of the cutting lips of the bit as compared with the apex angle of the original frusto-conical surfac of revolution of the bit blank I92. This reduction of the included angle of the cutting lip may b anticipated in the original formation of the frustoconical surface of the bit blank I92; that is, that angle may be made larger than the intended ultimate angle formed by the cutting lips of the finished countersinking bit.

Fig. 11 illustrates a suitable chuck 2H) for receiving the bit supporting element I9I of Fig. 10, the bit blank being still disposed therein as at I92. In the case of Fig. 11, however, wherein the object is to provide lip clearance for the bit, the disposition of the supporting element I9I and the bit blank I92 is concentric with respect to the axis of revolution of the chuck ZIII. A suitable cam 2 I2 is provided which is the same in principle as the cam I50 of the conventional drill bit grinding apparatus being modified only with respect to the relatively less angle of lip clearance which it is intended to provide. Both lip clearances of the bit blank I92 may be ground in a single revolution of the chuck 2I0, as in the case of grinding the lip clearances of conventional drill bits, by virtue of the fact that the cam 2I2 has two lip grinding inclines as in the case of the cam I50, whose contour is illustrated schematically in Fig. 9.

What is claimed is:

1. In a grinding machine, a base and a rotatable abrading implement carried thereby, supporting means likewise carried by said base and work holding means projecting from opposite ends thereof and journaled therein, one end of said holding means comprising a chuck for receiving a work piece and the other end of said holding means comprising a portion for manual manipulation, a cam secured to one of said means and a follower therefor on the other of said means, whereby the relative axial position of the holding means in the supporting means is automatically varied in response to manual rotation thereof, gage means carried by said base for engagement with the end of a work piece to be operated upon to align the same angularly on its own axis, said gage means being spaced from said abrading implement, and means providing pivotal movement of said work holding means whereby a work piece may be pivctally moved between said gage means and said abrading implement.

2. In a grinding machine, a rotatable abrading implement having a peripheral grinding face, r0- tatable work holding means, means for supporting said abrading implement and said work holding means with their axes in a common plane, said work holding means having a movable connection with said supporting means whereby it may be moved to and from operative position with respect to the abrading implement between abrading operations, automatic means for dressing the peripheral grinding face of said abrading implement between successive abrading operations and means for advancing the abrading implement toward the dressing means between abradin operations to compensate for the portion of the abrading implement removed during a dressing operation, said dressing means and said advancing means being actuable by and upon movement of said work holding means from operative position with respect to the abrading implement.

3. In a drill bit lip clearance grinding machine having a relatively fixed horizontally extending abrading line, an abrading wheel having a horizontal axis of rotation parallel to said line, means supporting said wheel for horizontal adjusting movement perpendicular to said axis and said line, wheel dressing means having a working face movable along said line to traverse the periphery of said wheel and dress it to coincidence with said line, means supporting a drill bit on an axis in the same horizontal plane as the axis of said wheel, said drill supporting means being pivoted on a vertical axis tangent to the periphery of said wheel, means for locking said supporting means in adjusted angular position on said pivot axis, means for automatically adjusting said wheel toward said abrading line and means for successively moving said dressing means along said line for dressing the periphery of said wheel between successive drill bit lip clearance grinding operations.

ARTHUR -A. SCHWARTZ. 

